Analysis of teeth reveals mammals once lived like reptiles
Analysis of teeth dating back 200 million years suggests that the earliest mammals functioned like reptiles - leading less active but much longer lives.
There search, led by the University of Bristol and University of Helsinki in Finland, is the first time palaeontologists have been able to study the physio logies of early fossil mammals directly.
Fossils of teeth from two of the earliest mammals, M or ga nu co don and Ku ehneotherium, which roamed the earth alongside early dinosaurs, were scanned using X-rays.
Researchers studied growth rings in the tooth sockets - deposited each year like tree rings - that could be counted to reveal how long the animals lived.
The results, published in Nature Communications, indicated a maximum lifespan of up to 14 years for the ani - mals.
This is much older than their similarly sized furry successors such as mice and shrews, which tend to only survive foray ear or two in the wild.
Dr Elis Newham, research associate at the University of Bristol, said: "We made some amazing and very surprising discoveries.
"It was thought the key characteristics of mammals, including their warm-bloodedness, evolved at around the same time.
"By contrast, our findings clearly show that, although they had bigger brain sand more advanced behaviour, they didn' t live fast and die young but led as lowerpaced, longer life a kin to those of small reptiles, like lizards."
Dr Pam Gill, senior research associate at the University of Bristol, was inspired to use advanced imaging technology on the teeth after a colleague had a tooth removed.
They told Dr Gill they wanted to get their tooth X-rayed, as it could reveal information about a person's life history.
"That got me wondering whether we could do the same to learn more about ancient mammals," Dr Gill said.
To test it, an ancient tooth specimen belonging to Morganucodon was sent to Dr Ian Corfe from the University of Helsinki. Dr Corfe used highpowered Synchrotron X-ray radiation to scan the tooth.